The Surgical Pathology and Postmorten Section, together with the Cytopathology Section, Ultrastructural Pathology Section and Hematopathology Section provide complete service in anatomic pathology for the Clinical center patients and collaborate with the research staff of all institutes in those investigations which involve the use and study of human pathological material. A new frozen section and surgical pathology processing area has been constructed adjacent to the new operating rooms and became operational on April 18, 1983. This new facility has greatly enhanced processing of specimens and communication of diagnostic findings with attending physicians. The staff is engaged in a variety of projects involving clinicopathological correlation and pathologic characterization of disease studied at the Clinical Center. Immunocytochemical techniques have been applied to the characterization and study of tumors and other non-neoplastic diseases. The use of immunohistochemical staining has greatly facilitated more precise diagnosis in selected difficult cases and with the increasing number of monoclonal antibodies available this technique should have even greater value in diagnostic and research pathology.